1. Field of the Invention
The invention relates to a superconducting cable system.
2. Description of Related Art
One such cable system is described in EP 0 326 923 B1.
In a cable system such as this, the cryostat is used as a sheath for the at least one superconducting electrical cable and the connecting areas thereof in end terminations. The aim is to ensure that the temperature of the cryogenic medium carried therein is maintained in the long term, and over relatively long distances as well, without significant heating. One such medium is, for example, nitrogen which, for example, is introduced into the cryostat at a temperature between 67 K and 90 K.
According to the initially cited EP 0 326 923 B1, the cryostat consists of two tubes, which enclose a gap between them, are composed of stainless steel, and can also be corrugated transversely with respect to their longitudinal direction, in which gap spacers composed of a material having low thermal conductivity and of plastic films coated with a metal and having high reflectivity are arranged between the two tubes, which spaces reduce the radiated heat. The gap is also evacuated. As long as the vacuum exists, a cryostat such as this can carry out its functions. However, if it collapses, for example as a result of damage to the outer tube of the cryostat, a sufficient amount of heat is introduced into the cryostat such that the operational reliability of the cable system is no longer ensured. The superconducting cable must then be disconnected immediately from the power supply system in order to prevent an electrical flashover from occurring in the cable system, because gas bubbles are formed in the cooling medium, in particular in nitrogen, because of the heat that is introduced. A flashover such as this would lead to destruction of parts of the cable system. This would lead to considerable damage, particularly in an end termination. The superconducting cable cannot be used again until the cryostat has been repaired. This requires a correspondingly large amount of effort.